An absorption cooling system provides a method of cooling using a primary heat source as a primary energy source. Absorption systems function in a similar manner to vapor compression systems. However, instead of using a compressor to compress refrigerant and supply the refrigerant to a condenser, absorption systems use a solution circuit. A solution circuit consists of an absorber and a generator (also known as a desorber) supplied with an absorbent. The absorbent absorbs the refrigerant in the absorber and desorbs the refrigerant in the generator, thus bringing the refrigerant from a low pressure, low temperature state to a high pressure, high temperature state. The generator then supplies the refrigerant to a condenser. Heat from a heat source is supplied to the generator during the desorbing process.
Multi-effect absorptions systems function in a similar manner to the basic single effect absorption system. However, they include at least a two generators and either an additional absorber, an additional condenser or both. Multi-effect absorption systems are more efficient than single effect absorption systems because they use dissipated heat from the additional absorber, additional condenser or both and apply that heat to one of the generators for use during the desorbing process. Absorption systems, both single-effect and multi-effect, may be implemented to cool rooms or data centers.
A data center may be defined as a location, e.g., room, that houses numerous printed circuit (PC) board electronic systems arranged in a number of racks. A standard rack may be defined as an Electronics Industry Association (EIA) enclosure, 78 in. (2 meters) wide, 24 in. (0.61 meter) wide and 30 in. (0.76 meter) deep. Standard racks may be configured to house a number of systems, e.g., about forty (40) systems, with future configurations of racks being designed to accommodate up to eighty (80) systems. The systems typically include a number of components, e.g., processors, micro-controllers, high speed video cards, memories, semi-conductor devices, and the like, that dissipate relatively significant amounts of heat during the operation of the respective components. For example, a typical system comprising multiple microprocessors may dissipate approximately 250 W of power. Thus, a rack containing forty (40) systems of this type may dissipate approximately 10 KW of power.
The power required to remove the heat dissipated by the components in the racks is generally equal to about 10 percent of the power needed to operate the components. However, the power required to remove the heat dissipated by a plurality of racks in a data center is generally equal to about 50 percent of the power needed to operate the components in the racks. The disparity in the amount of power required to dissipate the various heat loads between racks and data centers stems from, for example, the additional thermodynamic work needed in the data center to cool the air. In one respect, racks are typically cooled with fans that operate to move cooling fluid, e.g., air, across the heat dissipating components; whereas, data centers often implement reverse power cycles to cool heated return air. The additional work required to achieve the temperature reduction, in addition to the work associated with moving the cooling fluid in the data center and the condenser, often add up to the 50 percent power requirement. As such, the cooling of data centers presents problems in addition to those faced with the cooling of racks.
Conventional data centers are typically cooled by operation of one or more air conditioning units. The compressors of the air conditioning units typically require a minimum of about thirty (30) percent of the required cooling capacity to sufficiently cool the data centers. The other components, e.g., condensers, air movers (fans), etc., typically require an additional twenty (20) percent of the required cooling capacity. As an example, a high density data center with 100 racks, each rack having a maximum power dissipation of 10 KW, generally requires 1 MW of cooling capacity. Air conditioning units with a capacity of 1 MW of heat removal generally requires a minimum of 300 KW input compressor power in addition to the power needed to drive the air moving devices, e.g., fans, blowers, etc. Conventional data center air conditioning units do not vary their cooling fluid output based on the distributed needs of the data center. Instead, these air conditioning units generally operate at or near a maximum compressor power even when the heat load is reduced inside the data center.
In a similar manner to the compressors above, generators of an absorption system require a minimum amount of heating to provide a required cooling capacity to sufficiently cool the room or data center. Generally, heat input to the generator is not varied according to the distribution needs of the data center or according to its operating efficiency.
The substantially continuous operation of the air conditioning units is generally designed to operate according to a worst-case scenario. That is, cooling fluid is supplied to the components at around 100 percent of the estimated cooling requirement. In this respect, conventional cooling systems often attempt to cool components that may not be operating at a level which may cause their temperatures to exceed a predetermined temperature range. In addition, conventional return systems remove air from the data centers in an indiscriminate manner. That is, conventional return systems may remove relatively cool air from data centers and/or may not efficiently remove relatively warm air from data centers. Consequently, conventional cooling systems often incur greater amounts of operating expenses than may be necessary to sufficiently cool the heat generating components contained in the racks of data centers.